class_docstr: A stream operator that counts the number of non-missing values.
code: def forward(self) -> float:
      return self.func(self.inputs[0].value)
  
imports: from typing import Callable, List
  import numpy
  from tensortrade.feed.core.base import Stream
  from tensortrade.feed.api.float import Float
label_desc: Use image node_id 2 for calling the ExpandingCount obj's underlying member method code with example usage: obj.forward() and returns: self